This invention relates to methods and apparatus for cutting elastomeric materials at low skive angles, in particular cutting layered composites of elastomeric materials including layers containing reinforcing materials.
Various methods and apparatus have been used for the cutting of sheets of elastomeric material. Such elastomeric material might consist of single sheets of the homogeneous material, or multiple layered sheets of materials having properties that are different from one another. In the case of multiple layered sheets of elastomeric material that, for various reasons, need to be cut, one or more of the layers might contain reinforcing cords or fibers made of metal or fabric. Such reinforcing cords or fibers might be simply aligned in such a way as to be parallel to one another. Furthermore, the elastomeric materials that are to be cut may or may not be cured or vulcanized at the time of cutting.
Prior art cutting methods and apparatus include cutting wheels, ultrasonic cutters, guillotine knives, wire cutters and vibrating scroll cutters whose active cutting principle is a saw blade or a blade or a tensioned wire.
While such prior art cutting methods are effective to varying degrees, each has disadvantages. For example, the guillotine knife is somewhat effective in cutting composite elastomeric materials, but it has the disadvantage of having a tendency to deform the cut surfaces of the elastomeric material as the knife penetrates the material. Such deformation of the cut edge increases the difficulty of subsequent splicing the ends of the elastomeric material. Moreover, the guillotine knife produces a continually degraded cut surface as the blade becomes dull and as small pieces of elastomer began to build up on the blade. Yet another disadvantage was the inability of the blade to cut at an angle less than 30 degrees relative to the plane of the material being cut. The guillotine blade also tends to generate heat during the cutting process such that, as numerous cuts are made, the temperature of the knife becomes sufficiently elevated in some cases to induce precuring of unvulcanized elastomer in the region of the cut, which then inhibits subsequent proper splicing along the cut edges.
Another prior art cutting system and method, disclosed in U.S. Pat. No. 5,638,732, employs a cutting wire. This system could not, however, be used to cut preassembled elastomeric composite sheets containing reinforcing cords because the reinforcing cords themselves, though aligned more or less parallel to the direction of the cut, get severed. This deficiency is actually inherent to nearly every prior art cutting technology including ultrasonic knives, that cut composite elastomeric preassemblies at relatively low skive angles. That is to say, nearly all prior art cutting methods tended to cut the parallel-aligned cords that are used to reinforce one or more layers of reinforced ply. The cut is ideally intended to be made between the parallel-aligned reinforcing cords. One prior art exception is the scroll cutter, which can cut at low skive angles without also risking cutting the reinforcing cords.
The scroll cutter cannot, however, initiate its cut at a low skive angle through a cord reinforced sheet of preassembled composite elastomeric sheets, because of its geometry, which includes a wire held at each end by a fixture. The scroll cutter must start its cut from the side of the preassembly, such that the cutting has difficulty entering the ply without splitting the reinforcing cords. Even at a 90-degree skive angle, the reliability of not splitting cords is in question. At low skive angles it becomes exponentially difficult to enter the ply without splitting a ply cord. Sometimes the reinforced ply end will be buried under the other layers, such as, in the case of tire manufacturing, the sidewall layer or other layers such as the extreme edge of the preassembly within the context of envelope construction. This adds another dimension of difficulty for the wire scroll cutter to cut reliably a preassembly with reinforced layers, such as specifically, the ply of tires.
Ultrasonic cutting systems as disclosed in U.S. Pat. No. 5,265,508, can cut stock material at low skive angles. However, they require that the material be secured to an anvil during cutting. Another system, disclosed in U.S. Pat. No. 4,922,774, employs an ultrasonic cutting device, which vibrates a knife that moves across an elastomeric strip. However, this system is limited to cutting angles of between 10 and 90 degrees, and it does not provide for cutting between parallel disposed, reinforcement cords within the strip, which is to say, the cords can get cut.
Various method have been attempted to cut through cord-reinforced composites employing ultrasonic knives. In PCT publication No. WO 00/23261, a pair of ultra sonic blades are employed wherein after the article to be cut is pierced in a central region the two blades cut in opposite directions toward each lateral edge of the composite.
In PCT publication No WD 00151810 an ultrasonic skive cuts above the cord reinforced member as a cutting knife follows making a second cut through the ply and between parallel cords thus forming an abutment surface for subsequent tire splicing of the cut to length segment. Each of these concepts requires multiple cutting mechanisms and are arguable complex to build and maintain the equipment.
A significant problem with the prior art cutting systems and methods is the inability to cut at angles less than 30 degrees relative to the plane of the elastomeric layers being cut without deformation or precuring the material. This can be a problem in, for example, automated tire building operations wherein the cutting has to be done precisely and quickly and where the cutter can also provide improvements to the cut surface which is subsequently to be spliced.
An ideal cutting method and apparatus should be able to make cuts at low angles relative to the plane of the elastomeric sheet being cut, and it should be able to do so without cutting the parallel-aligned reinforcing cords between which the cutter is ideally to move. It should also be able to make these low angle cuts rapidly and reliably.
A method of cutting segments to desired lengths from the strip of elastomeric material as disclosed. The segments have a width W, elastomeric strips being formed of a plurality of tire components, at least one of the tire components being a cord reinforced component. The cords of the reinforced tire component are substantially parallel oriented in the direction of a cutting path formed across the width W.
The method has the step of moving an ultrasonic knife into cutting engagement of the elastomeric strip while supporting the strip along the cutting path. Cutting the segment at a skive angle xcex1. Impacting a cord of the cord reinforced component while cutting thereby lifting said cord over the ultrasonic knife as the segment is being cut. The impacted cord is at a cut end adjacent to the cutting path. The method further has the step of orienting a cutting edge on the ultrasonic knife inclined at an acute angle xcex8 relative to the strip-cutting path. In one embodiment of the invention, the method further has the step of movably restraining the strip ahead of the cutting.
The step of supporting the strip may further include supporting the strip at an angle xcex81 less than the skive angle xcex1 on one side of the cutting path and at an angle xcex82 greater than the skive angle on the opposite side of the cutting path. This causes the location of the impacted cord to occur approximately at the location wherein the supporting angle changes from xcex81 to xcex82.
In another embodiment the step of positioning the cutting edge of the ultrasonic knife includes the step of setting a gap distance (d) above the support approximately slightly less than or equal to the thickness of the cord reinforced component, along the region wherein the support is oriented at the angle xcex82. The method further includes forming one cut end of the segment wherein a plurality of cords is beneath and adjacent to a flat cut surface.
A segment formed by the method described above results in a first cut end having a cut splicing surface extending outward from the cord reinforced component and a second cut end having a plurality of cords beneath and adjacent to a flat cut surface. The segment, when the first cut end and the second cut end are joined, forms a lap splice having one or more overlapping cords.
An apparatus for cutting segments from a strip of multi-layered elastomeric material containing reinforcing cords, the cords being substantially parallel and more or less oriented in the direction of the cut path, is described by the following features. A cutting element for cutting the strip to form cut ends has a cutting edge oriented to cut along a line 3, the line 3 being tangent to one or more cords and inclined at a desired skive angle xcex1, and a means for supporting the strip along the cutting path, the means for supporting the strip having a first surface oriented at an angle xcex81 less than the skive angle xcex1, and a second surface oriented at an angle xcex82 greater than or equal to the skive angle xcex1, and a means for restraining the strip against the means for supporting, the means for restraining the strip preferably lying ahead of the cutting element, and being moveable. The apparatus further has a means for moving both the cutting element and the means for restraining during the cutting of the strip. In one embodiment, the apparatus has the cutting element having a cutting edge inclined at an acute angle xcex2 relative to the width of the strip. The cutting edge when oriented as described initiates cutting on the surface furthest away from the means for supporting the strip. The skive angle xcex1 is normally set about 10xc2x0 or less forming a cut path adjacent to one or more cords of the strip being cut. While the means or supporting the strip has two surfaces inclined at angles xcex8n, and xcex82 respectively, xcex81 is preferably set about 2xc2x0 less than the skive angle xcex1, the angle xcex82 is about 2xc2x0 more than the skive angle xcex1. In one embodiment the skive angle xcex1 is set to about 8xc2x0.
In a preferred embodiment the cutting element is an ultrasonic knife. The cutting element has a planer surface adjacent to the supporting means. The cutting element has a wedge shape increasing in thickness away from the cutting edge.
In a preferred embodiment the means for supporting the strip includes the vacuum-means for adhering the strip to the means for supporting during the cutting procedure.
xe2x80x9cAspect Ratioxe2x80x9d means the ratio of a tire""s section height to its section width.
xe2x80x9cAxialxe2x80x9d and xe2x80x9caxiallyxe2x80x9d means the lines or directions that are parallel to the axis of rotation of the tire.
xe2x80x9cBeadxe2x80x9d or xe2x80x9cBead Corexe2x80x9d means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers.
xe2x80x9cBelt Structurexe2x80x9d or xe2x80x9cReinforcing Beltsxe2x80x9d means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17xc2x0 to 27xc2x0 with respect to the equatorial plane of the tire.
xe2x80x9cBias Ply Tirexe2x80x9d means that the reinforcing cords in the carcass ply extend diagonally across the tire from bead-to-bead at about 25-65xc2x0 angle with respect to the equatorial plane of the tire, the ply cords running at opposite angles in alternate layers
xe2x80x9cBreakersxe2x80x9d or xe2x80x9cTire Breakersxe2x80x9d means the same as belt or belt structure or reinforcement belts.
xe2x80x9cCarcassxe2x80x9d means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.
xe2x80x9cCircumferentialxe2x80x9d means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction; it can also refer to the direction of the sets of adjacent circular curves whose radii define the axial curvature of the tread as viewed in cross section.
xe2x80x9cCordxe2x80x9d means one of the reinforcement strands, including fibers, which are used to reinforce the plies.
xe2x80x9cInner Linerxe2x80x9d means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
xe2x80x9cInsertsxe2x80x9d means the crescentxe2x80x94or wedge-shaped reinforcement typically used to reinforce the sidewalls of runflat-type tires; it also refers to the elastomeric non-crescent shaped insert that underlies the tread.
xe2x80x9cPlyxe2x80x9d means a cord-reinforced layer of elastomer-coated, radially deployed or otherwise parallel cords.
xe2x80x9cRadialxe2x80x9d and xe2x80x9cradiallyxe2x80x9d mean directions radially toward or away from the axis of rotation of the tire.
xe2x80x9cRadial Ply Structurexe2x80x9d means the one or more carcass plies or which at least one ply has reinforcing cords oriented at an angle of between 65xc2x0 and 90xc2x0 with respect to the equatorial plane of the tire.
xe2x80x9cRadial Ply Tirexe2x80x9d means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65xc2x0 and 90xc2x0 with respect to the equatorial plane of the tire.
xe2x80x9cSidewallxe2x80x9d means a portion of a tire between the tread and the bead.
xe2x80x9cSkivexe2x80x9d or xe2x80x9cskive anglexe2x80x9d refers to the cutting angle of a knife with respect to the material being cut; the skive angle is measured with respect to the plane of the flat material being cut.